feat: implement yaml functions based on helm implementation

[42atomys]

Description

We continue to backport features, bug fixes, and more from Sprig to Sprout. This time, I'm focusing on the YAML functions part, used by Helm and intended for use by others as well.

Changes

• Add fromYaml function to convert yaml string into a go map
• Add toYaml function to convert any to a yaml string
• Add mustFromYaml function to convert and return error to the template system when occurs
• Add mustToYaml function to convert and return error to the template system when occurs

Fixes Masterminds#358 Masterminds#360

Checklist

• I have read the CONTRIBUTING.md document.
• My code follows the code style of this project.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have updated the documentation accordingly.
• This change requires a change to the documentation on the website.

Additional Information

The documentation for the encoding part of the library will be released soon after this pull request on https://sprout.atom.codes

Initially implemented by @blakepettersson on sprig

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files	Coverage Δ
encoding_functions.go	100.0% <100.0%> (ø)
sprout.go	100.0% <100.0%> (ø)